This invention relates to down-hole tools, and in particular, though not exclusively, to a time delay mechanism for use with down-hole tools.
Down-hole pressure actuated or initiated devices which may be, for example, suspended from "pack-off" devices tubing or casing well conduit are known, per se. Typical "pack-off" devices include bridge plugs such as GB 2 261 895 B (Petroleum Engineering Services Limited), incorporated herein by reference.
Known cyclic/shear devices suffer from a number of problem. For example, maximum pressure application from above is normally limited with known devices. Furthermore, a well conduit may be provided with a number of pressure actuated or initiated devices throughout its entirety problems exist in testing one or more of these devices without accidentally activating another.